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Biomedical subjects

G C England

Publications and source records attributed to G C England.

At least 55 records · Page 3Linked to original sources
PubMed1997

Immunocytochemical localization of oestrogen and progesterone receptors in the uterus of the normal bitch during oestrus and metoestrus.

Frozen uterine biopsy samples obtained from eight bitches during oestrus and metoestrus were used to develop immunocytochemical methods for identifying steroid receptors. The use of anti-steroid receptor monoclonal antibodies DAKO ID5 and NCL-PGR resulted in reliable detection of oestrogen and progesterone receptors, respectively. The distribution and heterogeneity of both oestrogen receptor and progesterone receptor expression varied during the oestrous cycle. During oestrus, steroid receptor expression was greatest as indicated by a distinct and homogeneous distribution of nuclear staining within cells of the endometrial glandular and luminal epithelium and myometrium. In contrast, during metoestrus there was an overall reduction in both the number and intensity of staining of nuclei. Distribution and intensity of nuclear staining was heterogeneous. This reduction was obvious within the luminal epithelial cells where nuclear staining was negligible compared with that of the glandular epithelial cells. This method could be used for further receptor studies, particularly in those diseases mediated by steroid hormones such as cystic endometrial hyperplasia and mammary neoplasia.

Animals↗
PubMed1997

Progestogen concentration and ionic composition of the mammary secretion of periparturient bitches.

Mammary secretions were collected from nine bitches of various breeds during the periparturient period. Initial mean progestogen concentrations were high and started to decline from 5 days before parturition, in a similar way to changes in plasma progesterone concentration. Values were basal by 3-4 days after parturition. Marked individual and day variations prevented this method from reliably indicating the time of impending parturition. Calcium concentrations in milk increased from 3-5 days after parturition, whereas a decline in magnesium concentration was noted from day 1 postpartum. There was an increase in the Ca:Mg ratio from 1 day after parturition, although this was not significant until day 3, and was therefore not useful for predicting impending parturition. There were no significant changes in sodium concentration in milk.

Animals↗
PubMed1997

Urinary LH, plasma LH and progesterone and their clinical correlates in the periovulatory period of domestic bitches.

Ten bitches were examined daily from pro-oestrus until metoestrus to correlate endocrine, vaginoscopic and cytological assessments of stage of the oestrous cycle. It was considered that oocytes were fertile by 4 days after the LH peak assuming a 2 day lag before ovulation and a further 2 days for oocyte maturation. Eight bitches showed a plasma LH peak and five bitches showed a peak in urinary LH, which corresponded to the plasma LH peak. Plasma concentration of progesterone increased in all bitches. Initially, this coincided with the preovulatory LH peak and reached values of 7.7 +/- 0.6 ng ml-1 4 days later. The peak in number of a nuclear vaginal epithelial cells and the onset and peak of vaginal mucosal shrinkage with angulation occurred on average 2.4 +/- 1.5, 2.1 +/- 2.4, and 6.1 +/- 1.1 days after the plasma LH peak, respectively, giving sufficient precision to be of practical value in estimating the fertile period. However, the onset of vulval softening, changes in rectal temperature and colour of the vulval discharge varied considerably. Nine of the bitches were mated at the time of highest percentage of a nuclear cells, coinciding with the onset of the period of vaginal mucosal shrinkage with angulation. Eight became pregnant. Selected clinical parameters are therefore useful in predicting the optimal mating time of bitches, as is detection of plasma progesterone concentration higher than about 8 ng ml-1, but the latter appears to be the most reliable method. Detection of the urinary LH peak was more difficult and as yet offers no practical advantages except from the point of view of easy sample collection.

Animals↗
PubMed1996

Radiographic contrast medium for uterine insemination in the bitch, and its effect upon the quality and fertility of fresh dog semen.

Four ejaculates were collected from each of 6 adult male beagle dogs. The second fraction was divided into 3 aliquants which were then diluted with physiological saline, an isoosmolar solution of sodium/meglumine diatroate, and an iso-osmolar solution of iohexol. The diluted samples were incubated at 39 degrees C and evaluated at 0, 60, 90, 120, 240 and 360 min after dilution. A variety of assessments was made, including, spermatozoal motility, spermatozoal morphology, and acrosorne status. The practicality of using 1.0 ml of iso-osmolar contrast medium combined with radiographic examination was evaluated as a method of confirming accurate placement of a transcervical uterine catheter by injecting contrast after positioning the catheter in 4 beagle bitches. The effect of the procedure on fertility was assessed using 5 greyhound bitches which were inseminated with fresh semen and in which pregnancy was monitored using diagnostic B-mode ultrasound imaging. There was no significant difference between physiological saline and the sodium/meglumine diatroate solution upon semen quality, while the iohexol solution produced a significant reduction in spermatozoal motility and morphology. No adverse clinical effects were observed when contrast medium was administered into the uterus to either group of bitches. A subjective assessment of radiographic quality showed that the sodium/meglumine diatroate solution, which contained twice the iodine concentration of the iohexol solution, produced significantly greater radiopacity and was radiographically more useful than the iohexol solution. The sodium/meglurnine diatroate solution had no adverse effect upon the fertility of dog semen, and all bitches that were inseminated with this technique conceived and maintained the pregnancy to term. Litter size was considered to be normal for the breed. Small volumes of an iso-osmolar solution of sodium/meglumine diatroate may be useful for ensuring correct placement of transcervical catheters prior to artificial insemination in the bitch.

Journal Article↗
PubMed1996

Alpha 2 adrenoceptor agonists in the horse--a review.

In recent years the usefulness of the alpha 2 adrenoceptor agonist drugs has been recognized in equine practice. Several agents have become available and are now licensed for use in a number of countries. The principle actions of all alpha 2 adrenoceptor agonists are similar, in that they produce a reduction in heart rate and alteration of heart rhythm, an initial hypertension followed by a prolonged hypotension, a decrease in the cardiac output and respiratory depression. For clinical purposes, these agents produce sedation and analgesia, they are useful for premedication and markedly potentiate the effects of other sedative/analgesic agents. Differences in receptor specificity between the alpha 2 adrenoceptor agonists results in the distinguishing characteristics of the individual agents, particularly with respect to their duration of action, sedative effect and analgesic properties; their cardiopulmonary effects are however similar, when equipotent sedative doses are administered. When used in combination with other agents, the alpha 2 adrenoceptor agonists all appear to act in a similar manner, with the greatest difference being related to their duration of action.

Adrenergic alpha-2 Receptor Agonists↗
PubMed1996

Sedative effects of romifidine in the dog.

The sedative and physiological effects of intravenous romifidine at 0, 20, 40, 80 and 120 micrograms/kg were investigated in five clinically normal adult male beagle dogs in a blind study using a Latin square design. Following the injection of romifidine, the dogs became ataxic and stood with a wide-based stance, they exhibited signs of skeletal muscle relaxation and their heads were lowered. All the dogs became recumbent and there was a reduction in the heart and respiratory rates. Increasing the dose from 20 to 40 micrograms/kg, or higher, produced a significant reduction in heart rate. There was am increase in the sedation score following even low doses of romifidine, and although measures of sedation showed no differences among romifidine doses, subjectively, the higher doses produced a more consistent effect. Dogs given lower doses of romifidine regained a standing position more rapidly than following the higher doses, although this effect was not significantly different. A second blind study compared the sedative effects of intravenous romifidine, at 40 and 80 micrograms/kg, with medetomidine at 10 micrograms/kg in six adult beagles. The cardiopulmonary and sedative effects were not significantly different between all regimens, although medetomidine at 10 micrograms/kg appeared to be intermediate in effect between romifidine at 40 and 80 micrograms/kg. The sedative and physiological effects of romifidine in dogs appear to be similar to other alpha2-adrenoceptor agonists. Intravenous administration provided sedation which might be clinically useful.

Adrenergic alpha-Agonists↗
PubMed1996

Romifidine as a premedicant to propofol induction and infusion anaesthesia in the dog.

The effects of premedication with four different intravenous doses of romifidine (20, 40, 80 and 120 micrograms/kg bodyweight) and a saline placebo were compared in a group of 20 adult beagles of both sexes, undergoing anaesthesia with propofol for a clinical dental procedure. Anaesthesia was induced 10 minutes after premedication and maintained by intravenous infusion of propofol for a period of 30 minutes. Romifidine had a marked synergistic effect with propofol and reduced the required induction and infusion doses by more than 60 per cent for a standard level of anaesthesia; the synergistic effect was dose related. Following premedication, propofol produced no significant alteration of respiratory rate, heart rate or rectal temperature. Anaesthesia was found to be more stable following romifidine premedication at all doses studied. The quality of induction was unaltered by the dose of the romifidine. Recovery from anaesthesia was smooth and of a similar quality in all cases. There were no differences in the recovery times between the unpremedicated group and the dogs premedicated with any dose of romifidine studied. There were no adverse effects noted following this anaesthetic regimen. The marked dose-related synergism with propofol induction and infusion anaesthesia is relevant should romifidine be used in the dog in clinical veterinary practice.

Anesthesia, Dental↗
PubMed1995

Ultrasonographic diagnosis of non-palpable Sertoli cell tumours in infertile dogs.

Three previously fertile dogs were examined with a history of recent infertility. Semen evaluation revealed marked spermatozoal abnormalities, including lesions of the mid-piece region, poor spermatozoal motility and a low total spermatozoal output. The mean number of live normal spermatozoa was 21.1 +/- 17.4 x 10(6) spermatozoa. Examination of the testes with diagnostic B-mode ultrasound demonstrated solitary mass lesions which in each case were not palpable. Plasma oestrogen concentrations were elevated (mean, 43.0 +/- 8.5 pg/ml), and histologically the masses were shown to be Sertoli cell tumours. Several months after unilateral orchidectomy there was an increase in the percentage of normal spermatozoa and an increase in the spermatozoal motility and total spermatozoal output. The mean number of live normal spermatozoa was 149.8 +/- 22.9 x 10(6) spermatozoa and all the dogs subsequently returned to fertility. Ultrasonographic examination of the testes should be considered part of the routine investigation of the male reproductive tract.

Animals↗
PubMed1993

Ultrasonographic appearance of the ovary and uterus of the bitch during oestrus, ovulation and early pregnancy.

The ovaries and uteri of ten bitches were imaged daily from the onset of pro-oestrus until 30 days after the plasma surge of luteinizing hormone. During pro-oestrus small follicles increased in size but did not protrude above the surface of the ovary. Ovulation was characterized by a decrease in the number of fluid-filled follicles and their replacement with similarly sized hypoechoic structures. These structures declined in number after ovulation and were replaced by fluid-filled corpora lutea. Gradual thickening of the wall of the corpus luteum occurred with subsequent obliteration of the central anechoic cavity. During pro-oestrus and oestrus there was an increase in the transverse diameter of the uterus, which developed a characteristic appearance with central radiating areas of hyperechogenicity and zones of hypoechogenicity. These uterine changes were not considered to be specific enough to be used as an indication of ovulation. Uterine diameter and echogenicity did not differ between pregnant and non-pregnant bitches until gestational sacs were identified, a mean of 18.6 +/- 0.9 (SD) days after the plasma surge of luteinizing hormone. Embryonic tissue and heart beats were first detected between 23 and 27 days after the pre-ovulatory luteinizing hormone surge.

Animals↗
PubMed1993

Cryopreservation of dog semen: a review.

Success with artificial insemination of frozen dog semen has been limited. The major problems are associated with identifying the time of optimal fertility for insemination of the bitch, achieving intrauterine deposition of spermatozoa, the variation in post-thaw semen quality between individual dogs and poor spermatozoal survival after freeze-thawing. Many of these problems have been investigated and, to some extent, overcome; however, poor post-thaw spermatozoal longevity remains a problem and results from the lack of ordered logical studies of cryopreservation. The purpose of this paper is to review studies of dog spermatozoal preservation and insemination and to highlight those areas of cryopreservation that have been neglected.

Animals↗
PubMed1993

Hypo-osmotic swelling of dog spermatozoa.

Dog spermatozoa were evaluated for their ability to swell when exposed to hypo-osmotic conditions. A medium was developed to allow spermatozoal swelling to be identified easily; both the number of swollen spermatozoa and their morphological appearance were influenced by the characteristics of this medium. The number of swollen spermatozoa was inversely proportional to the number of dead spermatozoa in a sample. Although spermatozoal swelling was highly repeatable there was no correlation with spermatozoal motility, morphology or vital staining. Electron microscopic studies demonstrated that swelling of spermatozoa was characterized by ballooning of the tail membrane and internal flexion of the axial filaments. Spermatozoa with damaged membranes were unable to swell. Hypo-osmotic swelling of dog spermatozoa is reliable and repeatable and may be a useful assay for the diagnosis of spermatozoal membrane function.

Animals↗
PubMed1992

A comparison of the sedative effects of three alpha 2-adrenoceptor agonists (romifidine, detomidine and xylazine) in the horse.

The sedative effects of a new alpha 2-adrenoceptor agonist, romifidine, were compared with those of xylazine and detomidine. Five horses were treated with two doses of romifidine (40 micrograms/kg body weight and 80 micrograms/kg body weight), two doses of detomidine (10 micrograms/kg body weight and 20 micrograms/kg body weight) and one dose of xylazine (1 mg/kg body weight) given by intravenous injection using a Latin-square design. The dose of 80 micrograms/kg romifidine appeared equipotent to 1 mg/kg xylazine and 20 micrograms/kg detomidine, although at these doses both xylazine and detomidine had a shorter action. Detomidine 20 micrograms/kg and xylazine both produced greater lowering of the head and a greater degree of ataxia than romifidine at either dose. Romifidine produced sedation similar to that of the other drug regimes. The effect upon imposed stimuli was similar.

Acoustic Stimulation↗
PubMed1991

Comparison of the sedative effects of medetomidine and xylazine in horses.

The sedative effects in horses of the new alpha 2 agonist medetomidine were compared with those of xylazine. Four ponies and one horse were treated on separate occasions with two doses of medetomidine (5 micrograms/kg bodyweight and 10 micrograms/kg bodyweight) and with one dose of xylazine (1 mg/kg bodyweight) given by intravenous injection. Medetomidine at 10 micrograms/kg was similar to 1 mg/kg xylazine in its sedative effect but produced more severe and more prolonged ataxia, and one animal fell over during the study. Medetomidine at 5 micrograms/kg produced less sedation but a similar degree of ataxia to 1 mg/kg xylazine.

Animals↗